Caralynn is desperate to pee, but with Alisha already using the toilet, her only option is to pee in the shower in this video.

In this scene Alisha is using the toilet when Caralynn explodes into the bathroom, bursting to pee.  With the toilet occupied, and unable to wait a moment longer, Caralynn quickly strips off her pants as she steps into the shower, and lets go.  Standing in the shower, Caralynn pees down her legs and onto the tile floor as Alisha looks on, completely stunned.